In the UK, melatonin and trazodone sit on opposite sides of a legal line. Melatonin is an over-the-counter supplement you can buy today; trazodone is a POM-V medicine that your vet must prescribe, and in dogs it is used off-licence under the prescribing cascade. Melatonin is the sensible first step for mild, predictable stress — a restless night, a car journey, the groomer. Trazodone is for genuine phobia, post-operative crate rest, and diagnosed anxiety, and it needs a consultation.
British owners tend to hit this question in one of two ways: it's late October, Bonfire Night is coming, and last year was awful — or the practice has mentioned trazodone and you'd rather start with something gentler. Both are fair. Here is the honest comparison, in kilograms, with UK access realities included.
What's the difference between melatonin and trazodone?
Melatonin: a signal, not a sedative
Melatonin is a hormone your dog's pineal gland already produces on a light-dark cycle. Supplementing it reinforces the body's own "it's night now" message. It is sold over the counter as a complementary feed supplement, is not a controlled drug, and is generally described as non-habit-forming. What it will not do is knock a dog out. It lowers arousal and makes settling more likely — it does not overpower a dog already in full flight-or-fight.
Trazodone: a prescription medicine that genuinely sedates
Trazodone is a serotonin antagonist and reuptake inhibitor (SARI). There is no UK veterinary-licensed trazodone product for dogs, so vets prescribe the human medicine off-licence under the cascade — entirely legal and routine, but it means a clinical examination and an ongoing relationship with the practice. It is described in the Merck Veterinary Manual and by veterinary behaviourists as a common choice for situational anxiety and enforced rest. It produces visible sedation, which is both the point and the reason it is controlled.
The distinction that actually matters
Melatonin changes the conditions in which a dog can settle. Trazodone reduces a dog's capacity to stay wound up. If you need calmer, melatonin may be enough. If you need a Labrador to stay still on crate rest for six weeks after a cruciate repair, it will not be.
Melatonin vs trazodone: side-by-side
| Melatonin | Trazodone | |
|---|---|---|
| UK legal status | Over the counter, supplement | POM-V, prescribed off-licence under the cascade |
| How it works | Reinforces the natural sleep-wake signal | Modulates serotonin; produces sedation |
| Onset | ~15–30 minutes (liquid at the fast end) | ~1–2 hours; usually given 90 min ahead |
| Duration | ~8 hours | ~4–8 hours, highly variable |
| Strength | Mild — lowers arousal | Moderate to strong — visible sedation |
| Typical UK use | Restless nights, car travel, groomers, mild firework nerves, older dogs waking at 3am | Severe firework and thunder phobia, fear at the practice, post-op crate rest, diagnosed anxiety |
| Common side effects | Drowsiness, occasional mild tummy upset | Sedation, wobbliness, GI upset, panting, rarely paradoxical agitation |
| Serious risks | Very few; wide safety margin | Serotonin syndrome with other serotonergic drugs; cardiac and hepatic caution |
| Cost | Low — from about $21.99 a bottle, shipped free worldwide | Tablets are cheap; the consultation is the real cost |
| Access | Order today | Needs an appointment — book well before Bonfire Night |
When is melatonin the right first step?
- Restless nights. A dog that settles late, gets up repeatedly, or has drifted off a normal rhythm. This is what melatonin is genuinely built for.
- Car journeys. Mild anticipatory stress, given half an hour before you load up — particularly useful for long motorway runs and ferry crossings.
- Groomers, nail trims, visitors. Short, foreseeable stressors in a dog that is nervous rather than phobic.
- Mild firework nerves. A dog that pants and paces on Bonfire Night but isn't trying to dig through a door. A dog that is trying to dig through a door needs the vet, not a supplement.
- Older dogs with disrupted sleep. Often the first thing tried, alongside a check for arthritis pain or cognitive change. More in our guide to melatonin for senior dogs.
- Mild separation stress — as support alongside training, never as a replacement for it. See melatonin for dogs with separation anxiety.
Melatonin dosing by weight (metric)
Dosing goes by body weight. The ranges below reflect those cited by VCA Animal Hospitals, PetMD and the Merck Veterinary Manual, shown alongside the equivalent volume of a 3 mg/mL liquid.
| Dog's weight | Typical melatonin dose | Volume at 3 mg/mL | Maximum frequency |
|---|---|---|---|
| Under 4.5 kg (Chihuahua, Yorkie) | ≈ 1 mg | ≈ 0.33 mL | Up to 3× daily |
| 4.5–11 kg (Jack Russell, Cavalier) | ≈ 1.5 mg | ≈ 0.5 mL | Up to 3× daily |
| 12–45 kg (Springer, Labrador, GSD) | ≈ 3 mg | ≈ 1 mL | Up to 3× daily |
| Over 45 kg (Great Dane, Mastiff) | 3–6 mg | ≈ 1–2 mL | Up to 3× daily |
Give it about 30 minutes before bed or before the stressor, start at the low end, and allow three or four nights before judging. A fuller breakdown lives in our melatonin dosage for dogs chart.
When does your dog need trazodone instead?
Being honest about where melatonin stops is more useful than overselling it. Ring the practice when:
- Your dog is in genuine panic during fireworks or thunder — destroying doors, escaping, shaking uncontrollably, injuring itself.
- Your dog is on enforced crate rest after orthopaedic surgery and cannot be kept still by management alone.
- Visits to the surgery are so distressing that examination is unsafe for your dog or the team.
- A veterinary behaviourist has diagnosed an anxiety disorder needing medication.
- Melatonin and other non-prescription support have had a proper trial and haven't helped.
A practical UK note: October is the busiest month of the year for firework-anxiety appointments. If last November was bad, book in September or early October rather than the week of the fifth. Trazodone must not be combined casually with SSRIs, tramadol or other serotonergic medicines — the risk is serotonin syndrome — which is precisely why it is POM-V.
Can dogs have melatonin and trazodone together?
Some vets do use both, and melatonin is not serotonergic in the way tramadol or an SSRI is. But this is a decision for your vet, not a kitchen-table experiment. Both cause drowsiness, so combined sedation can exceed what you expect, and a dog on trazodone is by definition under veterinary management — anything you add should go through the same person. Ask at the appointment; it takes thirty seconds.
A melatonin worth starting with
If melatonin is the sensible first step, the formula matters. Human melatonin from a chemist is a poor fit: commonly 5 or 10 mg per tablet, impossible to split accurately for a Cavalier, and frequently sweetened with xylitol — acutely toxic to dogs.
Our Melatonin for Dogs – Calming & Sleep Support Drops ($21.99) is a liquid, so you measure 0.33 mL for a 4 kg terrier or 1 mL for a 30 kg Labrador from the same bottle. It is xylitol-free, made in North America under GMP conditions with a certificate of analysis on every batch, and every active is declared per millilitre rather than buried in a proprietary blend:
| Active ingredient (per 1 mL) | Amount | Commonly associated with |
|---|---|---|
| Melatonin | 3 mg | Sleep-wake cycle signalling |
| L-theanine | 50 mg | Relaxed alertness without sedation |
| Alpha-casozepine | 25 mg | Milk-derived peptide used in calming formulas |
| Chamomile extract (water-soluble) | 25 mg | Traditional calming herb |
| Magnesium (elemental) | 5 mg | Normal nerve and muscle function |
| Vitamin B6 (as P5P) | 0.5 mg | Cofactor in melatonin synthesis |
The multi-ingredient approach is deliberate: melatonin handles the sleep-cycle signal, while L-theanine and alpha-casozepine are the ingredients most commonly associated with daytime calm — which is where plain melatonin alone tends to disappoint owners. Liquid also absorbs faster than a chew that has to break down first, which matters when the first rocket goes up earlier than you planned. Compare options in our guide to the best melatonin for dogs and the broader dog calming and anxiety complete guide. Free worldwide shipping, so UK delivery costs you nothing extra.
Common mistakes UK owners make
- Expecting melatonin to behave like trazodone. If you need visible sedation, melatonin will look like a failure. It was never that tool.
- Leaving the vet appointment until the week of Bonfire Night. Practices are fully booked. Sort it in September.
- Using a human melatonin from the chemist. Check for xylitol before anything else — and note UK human melatonin is itself a prescription medicine, so this route is rarely as easy as owners assume.
- Dosing too late. Melatonin needs 30 minutes; trazodone usually 90. Given mid-panic, both underperform badly.
- Combining them without asking. Stacking two sedating agents yourself is how dogs end up wobbly and over-sedated.
- Treating medication as a substitute for management. Blackout curtains, sound masking, a den, and desensitisation work done in summer do more for firework phobia than any product given on the night.
When to ring your vet
Speak to the practice before starting anything if your dog is pregnant or nursing, is a puppy, is already on medication (particularly SSRIs, tramadol, sedatives or anticonvulsants), has heart, liver or kidney disease, or is diabetic.
Book promptly if anxiety is escalating rather than situational, if your dog is injuring itself or wrecking the house during storms or fireworks, if new night-time restlessness appears in an older dog (this can signal pain, cognitive dysfunction or an endocrine problem rather than a sleep issue), or if melatonin at a sensible dose has done nothing after two weeks.
Treat as an emergency — ring your vet or an out-of-hours service immediately — if a dog on trazodone becomes severely disoriented, tremors, develops a racing heart or collapses, or if your dog has eaten a human product containing xylitol. The Animal PoisonLine (01202 509000) is available to UK owners around the clock.
Frequently asked questions
Can I buy trazodone for my dog in the UK without a prescription?
No. Trazodone is a POM-V medicine and, because there is no UK veterinary-licensed product for dogs, your vet prescribes the human formulation off-licence under the cascade. That requires a clinical examination. Anyone selling it to you without one is not operating legally.
Is melatonin legal to give dogs in the UK?
Yes. Melatonin sold for dogs is a complementary feed supplement, available over the counter and widely used. Note that melatonin for human use is a prescription medicine in the UK, which is one more reason a dog-specific product is the simpler route.
Will melatonin be enough for Bonfire Night?
It depends entirely on severity. For a dog that pants, paces and hides but recovers, melatonin given 30 minutes before dusk — alongside a den, sound masking and closed curtains — is often enough. For a dog that panics, escapes or self-injures, it will not be, and that dog needs a veterinary plan made weeks in advance.
How much melatonin for a 10 kg dog?
A 10 kg dog sits in the 4.5–11 kg band, which corresponds to roughly 1.5 mg — about 0.5 mL of a 3 mg/mL liquid — up to three times daily, given around 30 minutes beforehand. Start at the low end and confirm with your vet, particularly if your dog is on any other medication.
If your dog's stress sits in the mild-to-moderate range — restless nights, car journeys, the groomer, distant fireworks — a properly built canine formula is the sensible place to start. Pure Majesty Pets Melatonin for Dogs – Calming & Sleep Support Drops is xylitol-free, declared per millilitre, made in North America with a COA on every batch, measurable to the drop for a 3 kg Chihuahua or a 50 kg Dane, and $21.99 with free worldwide shipping to the UK. If it isn't enough, you'll walk into the consult with far better information.
This article is for educational purposes only and is not a substitute for professional veterinary advice. Supplements are not intended to diagnose, treat, cure, or prevent any disease and have not been evaluated by the FDA or Health Canada. Always consult your veterinarian before adding melatonin or any supplement to your dog's routine, especially if your dog is pregnant, on medication, or has a health condition.